You could use the Reach to Survey the GCPs (Ground Control Points) - It functions as an RTK GPS with CM accuracy.
Most photogrammetry suites offer the use of coordinate systems and GCPs. I personally use Agisoft for my processing needs - it’s cost effective. The convenient part of the Phantom is it operates in WGS84, the same as the Reach - this would avoid coordinate transformations prior to aligning photos or selecting your GCPs.
There are several methods of performing the actual survey with the reach, multiple pieces of software and methodologies. The method you use will depend on your distance from your base typically - if you have long baselines you may require long single point observation times over each point. This can easily be done by recording the time spent over each of the ground control points and post processing each of the points based on time as a single observation in RTKPOST. In your case that may be the easiest method to use.
I would read through the Reach Documentation and check out the forum, there are various posts on surveying and the general use of the Reach.
I Would Start Here:
Reach for Land Surveying
Reach Documentation